GPS receiver with satellite frame synchronization process

• US 6,380,891 B1
• Filed: 03/24/2000
• Issued: 04/30/2002
• Est. Priority Date: 04/05/1999
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yamashita, Yuzo
• Primary Examiner(s): Louis-Jacques, Jacques H.
• Assistant Examiner(s): MANCHO, RONNIE M
• Application Number:
  US09/534,345
• Time in Patent Office: 767 Days
• Field of Search: 342/357.06, 342/357, 342/457, 342/458, 342/387, 342/356, 342/357.15, 342/463-465, 370/329, 370/330, 370/336, 370/343, 370/344, 370/380, 701/200-215, 340/572, 340/990, 340/995, 340/998, 375/219, 375/222, 375/377, 375/324, 375/334, 364/449.7, 364/449.8, 364/449.9, 364/450, 364/484, 364/460, 364/459, 364/726
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073

Abstract

A GPS receiver has a plurality of data demodulator circuits assigned to a plurality of GPS satellites, respectively, and a data memory which stores detailed orbit information of the GPS satellites. The GPS receiver searches for satellites the detailed orbit information of which was stored in the memory previously. When these searched GPS satellites are acquired, the GPS receiver executes satellite frame synchronization determination processing to check for an agreement among predetermined data included in satellite data transmitted from the acquired GPS satellites. When the searched GPS satellites cannot be acquired or the predetermined data do not agree, the GPS receiver executes a single-satellite frame synchronization determination processing to check for an agreement of predetermined data included in a plurality of frames of the satellite data. The GPS receiver starts positioning processing in response to an establishment of agreement to calculate its position.

Claims

1. A GPS receiver comprising:

acquisition means having a plurality of channels for acquiring a predetermined number of GPS satellites by searching for a corresponding GPS satellite by each of the channels;

time counting means for counting present time;

distance measuring means for extracting time information included in satellite data transmitted from the acquired GPS satellites, and measuring based on the extracted time information and the counted present time a distance of a present position from the GPS satellite which transmitted the satellite data;

positioning means for extracting detailed orbit information (Ephemeris) in the satellite data to calculate a position of the satellite and calculating a present position from the calculated satellite position and the measured distance;

memory means for storing the detailed orbit information so that the positioning means is enabled to execute a hot start in which the present position is calculated by using the stored detailed orbit information; and

synchronization means for executing satellite frame synchronization determination processing to establish a synchronization of the satellite data by checking for an agreement among predetermined data included in the satellite data transmitted from the plurality of GPS satellites when the plurality of GPS satellites, of which detailed orbit information is stored in the memory means, are acquired with in a predetermined time period from the time of executing the hot start.

2. A GPS receiver of claim 1, wherein:

when the plurality of GPS satellites corresponding to the stored detailed orbit information are acquired with in the predetermined time period but the predetermined data included in the satellite data of the acquired GPS satellites does not agree, the detailed orbit information stored in the memory means is erased and new detailed orbit information is acquired.

4. A GPS receiver of claim 1, wherein:

the acquisition means has at least four channels.

5. A GPS receiver of claim 1, wherein:

the acquisition means acquires at least three satellites for the satellite frame synchronization determination processing.

6. A GPS receiver of claim 1, wherein:

the memory means stores a general orbit data extracted from the satellite data and the present position calculated by the positioning means; and

the acquisition means searches for the GPS satellites based on the stored general orbit data, the present position and the counted time.

3. A GPS receiver comprising:

acquisition means having a plurality of channels for acquiring a predetermined number of GPS satellites by searching for a corresponding GPS satellite by each of the channels;

time counting means for counting present time;

distance measuring means for extracting time information included in satellite data transmitted from the acquired GPS satellites, and measuring based on the extracted time information and the counted present time a distance of a present position from the GPS satellite which transmitted the satellite data;

positioning means for extracting detailed orbit information (Ephemeris) in the satellite data to calculate a position of the satellite and calculating a present position from the calculated satellite position and the measured distance;

memory means for storing the detailed orbit information so that the positioning means is enabled to execute a hot start in which the present position is calculated by using the stored detailed orbit information; and

synchronization means for executing satellite frame synchronization determination processing to establish a synchronization of the satellite data by checking for an agreement among predetermined data included in the satellite data transmitted from the plurality of GPS satellites when the plurality of GPS satellites, of which detailed orbit information is stored in the memory means, are acquired with in a predetermined time period from the time of executing the hot start,

wherein the synchronization means executes a single-satellite frame synchronization determination processing when the acquisition means fails to acquire the plurality of GPS satellites the detailed orbit information of which are stored, the single-satellite frame synchronization determination processing being for checking for an agreement among predetermined data of a plurality of sub-frames included in the satellite data transmitted from a predetermined one of the satellites and for establishing a frame synchronization of the satellite data.

7. A method of processing GPS satellite data for position calculation by a GPS receiver, the method comprising:

searching for and acquiring a plurality of GPS satellites which are estimated to appear above the GPS receiver based on detailed orbit information previously stored in a memory of the GPS receiver;

receiving satellite data from the acquired plurality of GPS satellites by the GPS receiver;

extracting predetermined data included in a head part of each of the received satellite data;

checking for an agreement among the extracted predetermined data of the acquired plurality of GPS satellites; and

starting positioning processing to calculate a position of the GPS receiver by using another predetermined data included in the received satellite data of the plurality of GPS satellites.

8. A method of claim 7, wherein:

each of the satellite data includes a plurality of sub-frames, and a data of the first sub-frame is extracted to be checked with respect to the agreement.

9. A method of claim 7, wherein:

the searching and acquiring are executed with respect to at least three GPS satellites.

10. A method of claim 9, further comprising:

extracting predetermined data included in a plurality of sub-frames of the received satellite data of one of the acquired GPS satellites when the agreement of the extracted predetermined data does not hold.

11. A GPS receiver comprising:

an antenna for receiving radio signals from a plurality of GPS satellites;

a data demodulator circuit for demodulating the radio signals;

a high frequency process circuit for processing the radio signals;

a central processing unit that receives the radio signals, makes calculations based upon the radio signals and issues commands to the data demodulator;

a real time clock for counting the present time;

a memory unit for storing programs for executing various processing of the central processing unit;

wherein the central processing unit calculates the distance and angle of elevation from the receiver to one of the plurality of satellites based upon the radio signals and the present time determined by the real time clock or general orbit information stored in the memory unit;

wherein the distance and angle of elevation is stored in the memory unit and the central processing unit further able to calculate a future distance and angle of elevation based upon the distance and angle of elevation stored in the memory unit;

wherein if the central processing unit is able to receive radio signals from the plurality of satellites for which distance and angle data is stored in a predetermined time period, the central processing unit further executes a satellite frame synchronization determination process to establish a synchronization of the radio signals of each of the plurality of satellites by checking for an agreement among predetermined data included in the radio signals; and

wherein the central processing unit executes a single satellite frame synchronization process if the central processing unit is unable to receive radio signals from the plurality of satellites for which distance and angle data is stored.